Quantitative studies are being made on the covalent addition of nucleophilic reagents such as water, bisulfite ion, thiols, and amines to greater than C equals N-groups in heterocyclic molecules. In addition to calculating the magnitude of rate and equilibrium constants for these reactions, attempts are being made to correlate characteristics of the covalent addition reactions with characteristics of electro-chemical reductions of the same molecules. It is anticipated that the results of these studies will provide a rational basis for (a) the prediction of the stability of heterocyclic molecules with respect to covalent addition reactions (b) the making of rational decisions about the probability of these reactions occurring in biochemical reactions (c) the design of new drugs and (d) the chemical stabilization of drugs that are heterocyclic molecules. BIBLIOGRAPHIC REFERENCES: G.S. Rork and I.H. Pitman, "Bisulfite Ion Catalysed Degradation of 5-Fluorouracil," J. Pharm. Sci., 64, 2l6 (1975). G.S. Rork and I.H. Pitman, "A Kinetic Study of the Dehalogenation of 5-Halo-5, 6-dihydrouracils in Aqueous Solutions of Sodium Bisulfite," J. Amer. Chem. Soc., 97, 5566 (1975).